Boron-nitrogen compounds and process for the preparation thereof



United States Patent BORON-NITROGEN COMPOUNDS AND PROCESS FOR THEPREPARATION THEREOF Walter R. Hertler, Wilmington, Del., assignor to E.I.

du Pont de Nemours and Company, Wilmington, Del., a corporation ofDelaware No Drawing. Filed June 11, 1965, Ser. No. 463,335 US. Cl.260-5703 9 Claims Int. Cl. C07c 87/28, 85/00, 87/04 ABSTRACT OF THEDISCLOSURE Boron compounds which contain the anion wherein R and R areorganic groups and the charge is satisfied by quaternization of thenitrogen atom to form an inner salt, or by a cation, can be made byreacting B H with an isocyanide and further reacting the product RNH CBH with an hydroxide or with a hydrocarbylating agent. The compounds canbe used to prepare electrical resistors, and as reducing agents inpreparing printed electrical circuits.

This invention relates to novel boron-containing compounds and toprocesses for preparing them. More specifically, the invention relatesto C-substituted aminododecahydromonocarbaundecarborates and processesfor preparing them.

Increased activity in the preparation of novel polyhedral boroncompounds has become apparent, and in view of their many properties, thesearch for new polyhedral boron compounds has continued. It is an objectof this invention to provide for novel polyhedral boron compoundscontaining carbon as a part of the polyhedral framework. It is anotherobject to provide processes for making them. These and other objectswill become apparent hereinafter.

The novel compounds of this invention are represented by the formula 'nm m m wherein n is a whole number of 1-2, inclusive (i.e., 1 or 2); misa whole number of 01, inclusive (i.e., 0 or 1); and m+n is equal to 2; Ris alkyl, cycloalkyl (including monocyclic and polycyclic cycloalkyl) or'aralkyl; R is hydrogen, alkyl, cycloalkyl, aralkyl, in which the carbonatom bonded to the nitrogen in each of the three groups bears at leastone hydrogen (i.e., the R group is a primary or secondary group), orwhen n is less than 2, 0- or pnitro-substituted aryl; and M is oneequivalent of a cation defined further below. When n is 2, M of courseis not present and the two R groups may be alike or different.Preferably, they are alike.

The nucleus of the compounds of this invention is believed to be adistorted icosahedral fragment consisting of one carbon atom, ten boronatoms and two bridging hydrogen atoms. The substituted amino group isbonded to the carbon atom of the CB H nucleus.

The compounds of the invention can be viewed as salts or inner salts inwhich the anion is RR'NCB H The valence of the anion can be satisfied byanother R group or by the cation M.

ice

The compounds of the invention can be prepared as described by thefollowing equations:

( B10H14+RNC+ z m iz The product RNH CB H can be reacted with ahydroxide of the formula MOH MOH RNHzC B mHu RMNHC BmHn or with ahydrocarbyla ting reagent R Z R",z RNHzCBroHn RR"NHCB1QH11 RR"2NCB1oH1zReactions 2 and 3 are interchangeable, for example,

RRNHCB H can be treated with MOH to obtain RRMNCB H or RMNHCB H can betreated with R Z to obtain the same product. It is to be noted that R isdefined the same as R above, except that R cannot be hydrogen.

In the reaction of Equation 1, decarborane, obtained by well-knownprocedures, is treated with an isocyanide of the formula RNC where R isas previously defined.

The reaction can take place over a temperature range of about 25 C. toC. in an inert solvent. The solvent may be an aromatic hydrocarbon, suchas benzene or toluene; an aliphatic nitrile, such -as acetonitrile orpropionitrile; an aliphatic or alicyclic hydrocarbon, as for example,heptane, hexane, methylcyclopentane, or cyclohexane; an ether such asdioxane, tetrahydrofuran, or 1,2-dimethoxyethane, or an ester,exemplified by ethyl acetate, ethyl butyrate, Z-ethylhexyl propionate,and the like. Reaction time and pressures are not critical. Atmosphericpressures are generally employed for convenience.

Preferably, a hydrocarbon solvent is used, at a temperature of fromabout 60100 C. for a reaction time of about two hours. The ratio ofreactants is not critical, e.g., ratios of 10:1 and 1:10 may beemployed; but generally an excess of the isocyanide is preferred.

Exemplary isocyanides include methyl isocyanide, ethyl isocyanide,isopropyl isocyanide, isooctyl isocyanide, 3acholest-anyl isocyanide,and the like.

The products are isolated by conventional methods. In general, they areinsoluble in the reaction mixture, and may be isolated by filtration andrecrystallization. The products frequently are :solvated, e.g., withwater or dioxane. The solvating molecules can be removed by heating invacuo, e.g., at 20l35 C.

The process of the invention used to place R groups on the novelcompounds (covered by R in Formula 1) is a hydrocarbylation reactionemploying the hydrocarbylating reagent R Z, where R" has been definedpreviously and Z is a leaving group of valence g. The term leaving groupis used as described in Gould, Mechanism and Structure in OrganicChemistry, Holt-Dryden, 1959, p. 261. Preferably, Z is chloride,bromide, iodide, sulfate, or a C -C hydrocarbonsulfonate free ofaliphatic unsaturation, i.e., any unsaturation present is aromatic.Thus, examples of R" Z include dimethyl sulfate, methyl iodide, benzylchloride, methyl p-toluenesulfonate, ethyl p-nitrobenzenesulfonate,butyl methauesulfonate, isopropyl butanesulfonate, dodecylp-toluenesulfonate, and the like. This process is similar to andincludes the same reagents and, in general, the same hydrocarbyl groupsas are used to hydrocarbylate any organic amine, or hydrochloridethereof, and needs no further amplification. The hydrocarbylationproceeds rapidly at moderate temperatures (IS-45 C.) and atmosphericpressures.

The process employed to place the cation M in the compounds of thisinvention can be carried out with any compound of the formula RR'NHCB Hin the presence of a strong base. In basic solution the anion forms andthe salt RRMNCB H can be obtained. The cation M and the strong base canbe added together as an equivalent amount of the hydroxide MOH, and theresulting salt obtained by evaporation of the solvent. Alternatively,the boron reactant can be basified and the cation added as MX, where Xis an anion that gives a soluble salt in combination with the cation M.Preferably, for convenience, X is halogen.

M in these reactions and in the final M-containing products of thisinvention can be an alkali metal, alkaline-earth metal, .UU N+, U P+, US U As+, or U Sb+, wherein U is aliphatically saturated hydrocarbyl, andU is aliphatically saturated hydrocarbyl bonded to N through aliphaticcarbon. Preferably, U and U' each contain up to 18 carbon atoms and mostpreferably up to 12 carbons. Any two U or U groups, or a U and U in UU'N+ can also be joined (bonded) to each other directly or through anethereal oxygen atom to form a divalent aliphatically saturatedhydrocarbon group or oxygen-interrupted (mono-oxa) hydrocarbon group ofup to 18 carbon atoms and preferably of up to 12 carbons. Mostpreferably, this divalent group is an alkylene radical of 4-8 carbons.Aliphatically saturated hydrocarbyl is defined as a hydrocarbyl groupthat does not contain any aliphatic unsaturation, i.e., the hydrocarbylgroups can be alkyl, cycloalkyl, aryl, alkaryl or aralkyl.

Examples of the above cations include tetraisopentylammonium,heptyltrimethyla-mmonium, trimethylphenylammonium,cyclodedcyltrimethylammonium, tetramethylphosphonium,tetranaphthylphosphonium, ethylpentamethylene p tolylphosphonium,dimethyloctadecylsulfonium, methyltetramethylenesulfonium,triethylsulfoniurn, tetraphenylarsonium,benzylhexadecyldimethylarsonium, dodecyltriethylarsonium,tetr-amethylstibonium, N, N didodecylmorpholinium,dibenzyldimethylstibonium, and the like.

Of the above U- and U-substituted cations, the ammonium, phosphonium andsulfonium are preferred because of availability. For the same reason,those containing only lower alkyl (1-8 carbon atoms) are preferred.

The alkyl, cycloalkyl and aralkyl groups in R and R,

decahydronaphthyl, benzyl, l-phenylethyl, p-butyltolyl, p-

phenylphenethyl, 4-pyrenylmethyl, and the like. The carbon atom contentis not critical. However, the alkyl groups are preferably of up to 18carbon atoms, because of availability, and most preferably of up to 8carbons.

The cycloalkyl groups of R and R (and consequently,

of R") include alkylcycloalkyl and cycloalkylalkyl groups. Preferablythe R cycloalkyl groups contain from 4 to 30 carbon atoms; while the Rcycloalkyl groups contain 4 to 18 carbon atoms and most preferably 4-8.The aralkyl groups include alkaralkyl and preferably contain from 7-18carbon atoms.

The or p-nitro-substituted aryl groups of R' are preferably of 612carbon atoms and are exemplified by 0- nitrophenyl, p-nitrophenyl,I-(Z-nitronaphthyl), 2-(5-nitrobiphenylyl), and the like.

In general, the compounds of the invention are white, crystalline,high-melting solids which are stable to air, moisture and dilute acidsand bases.

The products and processes of the invention are illustrated in furtherdetail in the following examples.

4 EXAMPLE 1 A mixture of 10 g. of decaborane, 13.5 g. of n-butylisocyanide, and 150 ml. of benzene was refluxed for 2 hours, and thenevaporated in vacuo. The residue was washed with pentane and thenextracted with dilute aqueous sodium hydroxide. The extract wasacidified with hydrochloric acid, and the resulting precipitate wascollected by filtration to give 0.82 g. of n:C H NH CB HRecrystallization from benzene-methanol produced needles, M.P. 209210 C.

Analysis.Calcd. for C H B N: B, 52.6; H, 11.3; C, 29.2; N, 6.83. Found:B, 54.8; H, 11.3; C, 29.6; N, 7.03.

EXAMPLE 2 A mixture of 2.44 g. of decaborane, 2.34 g. of benzylisocyanide, and ml. of benzene was refluxed for 2 hours. The mixture wasevaporated in vacuo, and the residue was suspended in pentane andfiltered. The filter cake was extracted with dilute aqueous sodiumhydroxide and filtered. The filtrate was acidified with hydrochloricacid. The resulting precipitate was collected by filtration to give 1.02g. of C H CH NH CB H Recrystallization from benzene-cyclohexane followedby recrystallization from benzene-methanol gave crystals with M.P.180.5181 C.

Analysis.-Calcd. for C H B N: B, 45.2; H, 8.84; C, 40.1; N, 5.86. Found:B, 45.3; H, 8.73; C, 39.9; N, 5.75.

The product readily forms a crystalline 1:1 solvate with benzene fromwhich the benzene can be removed by heating in vacuo.

Platinum-catalyzed acid hydrolysis of a similar sample of the productgave 1859.2 ml. of hydrogen per gram of compound which corresponds to19.9 moles of H per mole of compound of molecular weight 239.5. This isconsistent with the equation:

and confirms the presence of 12 hydrogens on the CB nucleus.

EXAMPLE 3 A mixture of 4.9 g. of decaborone, 120 ml. of benzene, and 9g. of cyclohexyl isocyanide was heated to reflux, and 4 drops ofacetonitrile was added. After two hours refluxing, the mixture wascooled, and the precipitated solid collected by filtration. The crudeproduct was extracted with dilute aqueous sodium hydroxide solution andfiltered. The filtrate was acidified with hydrochloric acid whereupon acolorless precipitate appeared and was collected by filtration.Recrystallization from benzene containing a little ethanol gave 1.4 g.of C H NH CB H M.P. 2645-2665 C.

Analysis.Calcd. for C H B N: B, 46.7; H, 10.9; C, 36.4; N, 6.06. Found:B, 47.7; H, 11.0; C, 36.9; N, 6.10.

Platinum-catalyzed acid hydrolysis gave 1940.0 cc. of H per gram ofcompound which corresponds to 20 moles of H per formula wt. 231.5 inaccord with the equation C H NHzCB oH z 3 CGHHNHCHS 10B (OH) 3 Thisconfirms the presence of 12 hydrogens on the CB nucleus.

When a similar sample of CGHllNHZCBloHlZ was dissolved in alkaline D 0and then precipitated with acid, the infrared spectrum of the productshowed no B-D absorption; however, the absorption characteristic of NH;stretch and NH deformation had disappeared, and new peaks characteristicof ND stretch and deformation had appeared. This confirms the presenceof two hydrogens on the nitrogen atom.

EXAMPLE 4 A mixture of 2.44 g. of decaborane, 3.32 g. of tertbutylisocyanide, and ml. of benzene was stirred at reflux for 2 hours. Themixture was cooled and filtered to give a solid material. The filtratewas treated with pentane which caused precipitation of additional solidmatreial. The combined solids were extracted with dilute aqueous sodiumhydroxide solution and the mixture was filtered. The filtrate wasacidified with hydrochloric acid and the resulting precipitate collectedby filtration to give 1.07 g. of (CH CNH CB H Recrystallization frombenzene-ethanol gave pale yellow plates, M.P. 233- 234 C.

Analysis.Calcd. for C H B N: B, 52.6; H, 11.3; C, 29.2; N, 6.8. Found:B, 52.1; H, 11.5; C, 29.9; N, 7.1.

The H nuclear-magnetic-resonance (n-m-r) "spectrum of the product inacetone-d shows a single peak at 8.89 1- corresponding to the tert-butylgroup. No other peaks were detected.

The mass spectrum of a similar sample (solid injec tion) showed a peakat 207 as the highest significant peak corresponding to C H- B N of all13 isotope.

EXAMPLE 5 l-isocyanoadamantane was prepared in the following manner: Toa solution of 9.17 g. of l-formamidoadamantane in 31 ml. of pyridine and16 ml. of petroleum ether was added 4.7 g. of phosphorus oxychloride,whereupon a vigorous reaction ensued. The resulting mixture was refluxedfor minutes and then treated with ice water and filtered to give 5.02 g.of l-isocyanoadamantane as a pale tan solid. An additional crop of 3.5g. was obtained by evaporation of the organic phase of the filtrate.Recrystallization from heptane gave crystals of l-isocyanoadamantane,M.P. 190191 C.

Analysis-Calm. for C H N: C, 81.9; H, 9.4; N, 8.7. Found: C, 82.0; H,9.5; N, 8.7.

The infrared absorption spectrum of the product showed an intense peaknear 2100 cm? characteristic of the isocyano group.

A mixture of 5 g. of l-isocyanoadamantane, 5 g. of decaborane and 75 ml.of benzene was stirred at reflux for 1 hour. The mixture was cooled andfiltered to give 3.5 g. of crude l-C H NH cB H as a tan solid.Recrystallization of the product from benzene-cyclohexane gave 1.78 g.of pure 1-C I-I -NH CB H which darkens but does not melt to 500 C.

Analysis.Calcd. for C H B N: B, 38.2; H, 10.3; C, 46.6; N, 4.94. Found:B, 38.8; H, 10.5; C, 48.9; N, 4.99.

The infrared spectrum of the product shows absorption at 3150 and 1560cm." characteristic respectively of -NH stretch and -NH deformation,consistent with the proposed structure.

EXAMPLE 6 To a warm stirred solution of 0.175 g. of

C6H11NH2CB1OH12 in 5% aqueous sodium hydroxide was added dropwisedimethyl sulfate. A precipitate soon formed and was collected byfiltration to give 0.195 g. of

s 11 3)z 1o 12 as a white solid. Recrystallization frombenzene-ethanolcyclohexane gave crystals of M.P. 255-257 C.

Analysis.-Calcd. for C H B N: B, 41.8; H, 11.3; C, 41.6; N, 5.4. Found:B, 41.7; H, 11.3; C, 42.1; N, 5.4.

Example 7 as a yellow solid. The product was purified byrecrystallization from benzene-cyclohexane to give colorless crystals,M.P. 157159 C.

6 Analysis.-Calcd. for CqHgqBmNI B, 46.4; H, 11.7; C, 36.0; N, 6.0.Found: B, 46.9; H, 11.6; C, 35.3; N, 6.4.

Example 8 To a filtered solution of 0.5 g. of (CH CNH CB H in diluteaqueous sodium hydroxide solution was added an excess oftetramethylammonium chloride. The resulting precipitate was collected byfiltration and recrystallized from aqueous ethanol containing a littletetramethylammonium hydroxide to give 0.31 g. of

as plates, M.P. 203-208 C.

Analysis.Calcd. for C9H34B10N22 B, H, C, 38.8; N, 10.1. Found: B, 38.5;H, 12.1; C, 38.7; N, 10.1. The H n-m-r spectrum of the product inacetonitile-d showed two peaks at 7.181- (tetramethylammonium, relativeintensity 4) and 9.181 (tert-butyl, relative intensity 3). No otherpeaks were observed.

Example 9 To a solution of 0.5 g. of CgHnNHgCBmHm in dilute aqueoussodium hydroxide was added tetramethylammonium chloride. The resultingprecipitate was collected by filtration to give 0.46 g. of

as a white solid. Recrystallization from aqueous ethanol gave crystalswith M.P. 21 6-219 C.

Analysis.CalCd. for C11H35B10N2: B, H, C, 43.4; N, 9.19. Found: B, 37.3;H, 11.8; C, 42.5; N, 8.71.

Example 10 To a solution of 0.2 g. of C H CH NH CB H in dilute aqueoussodium hydroxide solution was added excess aqueous rubidium chloride.The resulting precipitate was collected by filtration and recrystallizedfrom aqueous sodium hydroxide containing rubidium chloride to givecrystals of RbC H CH NHCB H -H O.

Analysis.Calcd. for CgHggBloNORbI B, 31.6; H, 6.5; C, 28.1. Found: B,31.8; H, 6.4; C, 27.3.

The foregoing examples are merely illustrative, for any of the R, R andM groups described hereinabove may be placed on the NCB H nucleus by theprocedures described in the examples.

The compounds of the invention are useful as reducing agents. Forexample, they reduce silver nitrate to metallic silver.

They are also useful as intermediates in the preparation of other boroncage compounds. For example, 0.82 g.

of (CH CNH CB H 30 ml. of di(2-methoxyethyl) which was collected byfiltration and recrystallized from aqueous ethanol containingtetramethylammonium hydroxide. The resulting plates melted at 345-349 C.with concomitant bubbling.

Analysis.-Calcd. for C H B N B, 41.3; H, 11.5; C, 37.5; N, 9.71. Found:B, 41.0; H, 12.0; C, 37.3; N, 9.77.

The compounds of the invention are also useful in the preparation ofelectrical resistors. A cotton string can be impregnated with a nearlysaturated solution of a compound of the invention, e.-g., (CH CNH CB Hin a volatile solvent such as acetonitrile. When the string is removed,dried and burned, a coherent ash is left which resembles the originalstring in size and shape. This ash is sufiiciently coherent to permitembedding in paralfin for use as an electrical resistor. Resistors of upto 4200 ohms/mm. have been prepared in this fashion.

The novel compounds can be employed as reducing agents in preparingprinted electrical circuitry. A circuit can be traced on paper using asolution of acetonitrile and one of the compounds of this invention.After evaporating the solvent, the tracings can be sprayed with anaqueous solution of palladium chloride. After rinsing, a metallictracing of reduced palladium is left.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

The embodiments of this invention in which the exclusive property orprivilege is claimed are defined as follows:

1. A compound of the formula RR NCB H wherein R is selected from thegroup consisting of alkyl up to 18 carbons, cycloalkyl of from 430carbons and aralkyl of from 7-18 carbon atoms;

R' is selected from the group consisting of hydrogen, alkyl of up to 18carbons, cycloalkyl of from 4-18 carbon atoms, aralkyl of from 7-18carbon atoms, wherein said alkyl, cycloalkyl and aralkyl groups arebonded to the nitrogen atom through a carbon bearing at least onehydrogen.

2. A compound of claim 1 wherein R is hydrogen.

8. A process for preparing boron compounds which comprises reacting RNHCB H wherein R is selected from the group consisting of alkyl of up to18 carbon atoms, cycloalkyl of from 430 carbon atoms, and aralkyl offrom 7-18 carbon atoms, with a composition selected from the groupconsisting of R" Z, wherein R is selected from the group consisting ofalkyl of up to 18 carbon atoms, cycloalkyl of from 4-18 carbon atoms,aralkyl of from 7-18 carbon atoms, o-nitroaryl, p-nitroaryl, oandp-nitroaryl, said aryl groups having 6-12 carbon atoms, and wherein saidalkyl, cycloalkyl and aralkyl groups are bonded to the nitrogen atomthrough a carbon bearing at least one hydrogen; Z is the leaving groupof hydrocarbylating reagent R" Z; and g is the valence of Z.

9. A process for preparing boron compounds which comprises reactingdecaborane with an isocyanide of the formula RNC, wherein R is selectedfrom the group consisting of alkyl of up to 18 carbon atoms, cycloalkylof from 4-30 carbon atoms, and aralkyl of from 7-18 carbon atoms, in aninert solvent at a temperature between 25 C. and 140 C.

References Cited UNITED STATES PATENTS 3,203,995 8/1965 Green et al.260583 CHARLES E. PARKER, Primary Examiner.

R. L. RAYMOND, Assistant Examiner.

US. Cl. X.R.

